Method and apparatus for reading code using short-range millimeter wave (mmwave) radar

ABSTRACT

A code reading method and a radar system using a short-range millimeter wave (mmWave) radar are provided. The method includes transmitting a mmWave radar signal to a target object from a radar system and receiving a reflection wave signal reflected on the target object, extracting reflection signal strengths for a plurality of line codes constituting the target object from the reflection wave signal, compensating for the reflection signal strengths considering a difference in antenna gain between the plurality of line codes as per an antenna radiation pattern of the radar system, forming a radar image using the compensated reflection signal strengths, and reading a binary code from the radar image.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation application of prior application Ser.No. 15/449,498, filed on Mar. 3, 2017, and was based on and claimedpriority under 35 U.S.C. § 119(a) of a Korean patent application number10-2016-0025455, filed on Mar. 3, 2016, in the Korean IntellectualProperty Office, the disclosure of which is incorporated by referenceherein in its entirety.

TECHNICAL FIELD

The present disclosure relates to methods and apparatuses for extractingimages of conductive objects using millimeter wave (mmWave) radar.

BACKGROUND

Radar means technology that detects an object using electromagnetic (EM)scattering and the range, speed, and shape of the object. In otherwords, a radar transceiver detects reflection wave signals backscatteredfrom an object and calculates a radar cross section (RCS) of the objectbased on the signal strength of the reflection wave signals. The RCS isa parameter indicating how big a target object is seen on a radar andvaries depending on the dielectric constant, shape, angle, and frequencyof the target object.

Typical EM radar imaging has been developed and used for purposes ofdistance measurement, targeting, and tracking. The size in which a radaris mounted may reach a few meters. Since several years ago,communication systems using millimeter waves (mmWave) with a frequencyof 30 GHz or more and a wavelength of 1 cm or less have been researched,leading to the implementation of 1 cm or less-sized micro antennas. Suchmicro antennas happened to be equipped in a transceiver, allowing forimplementations of tiny semiconductor chip-type radars and variousapplications using the same.

In developing an application technology using short-range mmWave radar,it is critical to compensate for the strength of reflection wave signalsintended for calculating a RCS (hereinafter, simply “reflection signalstrength”). More particularly, 1 m-long or less short-range radars maybe subject to a distortion of reflection wave signals by themaximum-minimum distance difference between the radar and the target. Asignal attenuation in a radar system is proportional to the power offour. Thus, a slight difference in the maximum-minimum difference maycause a significant distortion of a radar image within a short range.Such issue could be disregarded given the fact that radar systemsaccording to the related art have mostly accounted for long-distanceobject detection because the maximum-minimum distance differencerelative to the distance to the target is neglectably small. Forexample, when the distance between a radar and a target is a few tens ofkm, and the size of the object is several meters, the object would beseen like a dot when viewed from the radar. However, if a short-rangeradar, a few tens of cm away from a target object looks at a fewcentimeter size object, the difference in strength between signalsreflected on the same surface of an object needs to be compensated dueto the difference in strength between the earliest reflection signalcoming from the object and the latest coming reflection signal.

The above information is presented as background information only toassist with an understanding of the present disclosure. No determinationhas been made, and no assertion is made, as to whether any of the abovemight be applicable as prior art with regard to the present disclosure.

SUMMARY

Aspects of the present disclosure are to address at least theabove-mentioned problems and/or disadvantages and to provide at leastthe advantages described below. Accordingly, an aspect of the presentdisclosure is to provide a method and an apparatus for implementing anapplication technology using a short-range radar system.

Another aspect of the present disclosure is to provide a method and anapparatus for compensating for reflection signal strengths in amillimeter wave (mmWave) radar system.

In accordance with an aspect of the present disclosure, a method and anapparatus for predicting and compensating for factors that affect theradar cross section (RCS) in a mmWave radar system are provided.

In accordance with another aspect of the present disclosure, a methodand an apparatus for reducing a RCS distortion in a short-range radarsystem are provided.

In accordance with another aspect of the present disclosure, a methodand an apparatus for reading a conductor code by synthesizing a radarimage of the conductor code in a short-range radar system are provided.

In accordance with another aspect of the present disclosure, a methodfor reading a code using a short-range mmWave radar is provided. Themethod includes transmitting a mmWave radar signal to a target objectfrom a radar system and receiving a reflection wave signal reflected onthe target object, extracting reflection signal strengths for aplurality of line codes constituting the target object from thereflection wave signal, compensating for the reflection signal strengthsconsidering a difference in antenna gain between the plurality of linecodes as per an antenna radiation pattern of the radar system, forming aradar image using the compensated reflection signal strengths, andreading a binary code from the radar image.

In accordance with another aspect of the present disclosure, a radarsystem reading a code using a short-range mmWave radar is provided. Theradar system includes a transceiver configured to transmit a mmWaveradar signal to a target object and receiving a reflection wave signalreflected on the target object and a processor configured to extractreflection signal strengths for a plurality of line codes constitutingthe target object from the reflection wave signal, compensate for thereflection signal strengths considering a difference in antenna gainbetween the plurality of line codes as per an antenna radiation patternof the radar system, form a radar image using the compensated reflectionsignal strengths, and read a binary code from the radar image.

Other aspects, advantages, and salient features of the disclosure willbecome apparent to those skilled in the art from the following detaileddescription, which, taken in conjunction with the annexed drawings,discloses various embodiments of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The patent or application file contains at least one drawing executed incolor. Copies of this patent or patent application publication withcolor drawing(s) will be provided by the Office upon request and paymentof the necessary fee. As the color drawings are being filedelectronically via EFS-Web, only one set of the drawings is submitted.

The above and other aspects, features, and advantages of certainembodiments of the present disclosure will be more apparent from thefollowing description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a view illustrating an application technology using ashort-range millimeter wave (mmWave) radar according to an embodiment ofthe present disclosure;

FIG. 2 is a view illustrating operations of a radar transceiveraccording to an embodiment of the present disclosure;

FIG. 3 is a view illustrating a tag cross polar electromagnetic (EM)image detected by a radar transceiver according to an embodiment of thepresent disclosure;

FIG. 4 is a view illustrating an operation of determining a scan time ofa target moving at a constant velocity in a radar system according to anembodiment of the present disclosure;

FIG. 5 is a view illustrating an operation of determining a scan time ofa target moving at a variable velocity in a radar system according to anembodiment of the present disclosure;

FIG. 6 is a block diagram illustrating a brief structure of a radarsystem according to an embodiment of the present disclosure;

FIG. 7 is a view illustrating differences in reflection signal strengthdue to distances between a shrunken running screen and a target objectaccording to an embodiment of the present disclosure;

FIG. 8 is a view illustrating differences in reflection signal strengthdue to antenna radiation patterns in a shrunken running screen accordingto an embodiment of the present disclosure;

FIG. 9 is a flowchart illustrating a code reading procedure using ashort-range mmWave radar system according to an embodiment of thepresent disclosure;

FIGS. 10A, 10B, and 10C are views illustrating a correction procedure ofa radar image according to an embodiment of the present disclosure; and

FIG. 11 is a view illustrating a procedure of reading a binary code froma compensated radar image according to an embodiment of the presentdisclosure.

Throughout the drawings, it should be noted that like reference numbersare used to depict the same or similar elements, features, andstructures.

DETAILED DESCRIPTION

The following description with reference to the accompanying drawings isprovided to assist in a comprehensive understanding of variousembodiments of the present disclosure as defined by the claims and theirequivalents. It includes various specific details to assist in thatunderstanding but these are to be regarded as merely exemplary.Accordingly, those of ordinary skill in the art will recognize thatvarious changes and modifications of the various embodiments describedherein can be made without departing from the scope and spirit of thepresent disclosure. In addition, descriptions of well-known functionsand constructions may be omitted for clarity and conciseness.

The terms and words used in the following description and claims are notlimited to the bibliographical meanings, but, are merely used by theinventor to enable a clear and consistent understanding of the presentdisclosure. Accordingly, it should be apparent to those skilled in theart that the following description of various embodiments of the presentdisclosure is provided for illustration purpose only and not for thepurpose of limiting the present disclosure as defined by the appendedclaims and their equivalents.

It is to be understood that the singular forms “a,” “an,” and “the”include plural referents unless the context clearly dictates otherwise.Thus, for example, reference to “a component surface” includes referenceto one or more of such surfaces.

By the term “substantially” it is meant that the recited characteristic,parameter, or value need not be achieved exactly, but that deviations orvariations, including for example, tolerances, measurement error,measurement accuracy limitations and other factors known to those ofskill in the art, may occur in amounts that do not preclude the effectthe characteristic was intended to provide.

For the same reasons, some elements may be exaggerated or schematicallyshown. The size of each element does not necessarily reflect the realsize of the element. The same reference numeral is used to refer to thesame element throughout the drawings.

Advantages and features of the present disclosure, and methods forachieving the same may be understood through the various embodiments tobe described below taken in conjunction with the accompanying drawings.However, the present disclosure is not limited to the variousembodiments disclosed herein, and various changes may be made thereto.The various embodiments disclosed herein are provided only to inform oneof ordinary skilled in the art of the category of the presentdisclosure. The present disclosure is defined only by the appendedclaims. The same reference numeral denotes the same element throughoutthe specification.

It should be appreciated that the blocks in each flowchart andcombinations of the flowcharts may be performed by computer programinstructions. Since the computer program instructions may be equipped ina processor of a general-use computer, a special-use computer or otherprogrammable data processing devices, the instructions executed througha processor of a computer or other programmable data processing devicesgenerate a method for performing the functions described in connectionwith a block(s) of each flowchart. Since the computer programinstructions may be stored in a computer-available or computer-readablememory that may be oriented to a computer or other programmable dataprocessing devices to implement a function in a specified manner, theinstructions stored in the computer-available or computer-readablememory may produce a product including an instruction means forperforming the functions described in connection with a block(s) in eachflowchart. Since the computer program instructions may be equipped in acomputer or other programmable data processing devices, instructionsthat generate a process executed by a computer as a series of operationsare performed over the computer or other programmable data processingdevices and operate the computer or other programmable data processingdevices may provide operations for executing the functions described inconnection with a block(s) in each flowchart.

Further, each block may represent a module, segment, or part of a codeincluding one or more executable instructions for executing a specifiedlogical function(s). Further, it should also be noted that in somereplacement execution examples, the functions mentioned in the blocksmay occur in different orders. For example, two blocks that areconsecutively shown may be performed substantially simultaneously or ina reverse order depending on corresponding functions.

As used herein, the term “unit” means a software element or a hardwareelement, such as a field-programmable gate array (FPGA) or anapplication specific integrated circuit (ASIC). A unit plays a certainrole. However, the term “unit” is not limited as meaning a software orhardware element. A ‘unit’ may be configured in a storage medium thatmay be addressed or may be configured to reproduce one or moreprocessors. Accordingly, as an example, a ‘unit’ includes elements, suchas software elements, object-oriented software elements, class elements,and task elements, processes, functions, attributes, procedures,subroutines, segments of program codes, drivers, firmware, microcodes,circuits, data, databases, data architectures, tables, arrays, andvariables. A function provided in an element or a ‘unit’ may be combinedwith additional elements or may be split into sub elements or sub units.Further, an element or a ‘unit’ may be implemented to reproduce one ormore central processing units (CPUs) in a device or a securitymultimedia card.

Although the description of various embodiments herein primarily focuseson examples of a particular system, the subject matter of the presentdisclosure may also be applicable to other communication systems orservices having similar technical backgrounds without departing from thescope of the present disclosure, and this may be determined by one ofordinary skill in the art.

Proposed is technology capable of synthesizing a radar image utilizing asingle transceiver in order to apply a short-range millimeter wave(mmWave) radar to a chipless radio frequency identification (RFID)system according to various embodiments of the present disclosure.

According to an embodiment of the present disclosure, a short-rangemmWave radar system may be used to identify a product box, which is anon-conductive wrapping material, under the circumstance where theproduct box is conveyed on a conveyor belt in a warehouse ormanufacturing factory, with a tag for a chipless mmWave radar embeddedtherein or attached on the outside thereof. In order to secure a radarimage of the box moving at a constant velocity or variable velocity,reflection signals may be measured at times when it is equi-angularlypositioned with respect to the position of the radar system having asingle transceiver. The following embodiments encompass technologycapable of real-time detection of the optimal measurement time ensuringequi-angularity.

FIG. 1 is a view illustrating an application technology using ashort-range mmWave radar according to an embodiment of the presentdisclosure. An example chipless RFID is shown here which reads a barcodeusing a radar.

Referring to FIG. 1, a conveyor belt 120 may convey products at apredetermined velocity. A radar transceiver 110 with a singletransceiver is positioned within a predetermined short distance from themoving line along which the products are conveyed on the conveyor belt120. The radar transceiver 110 transmits a radar signal 140 to theconveyor belt 120, receives a reflection wave signal 145 reflected bythe conductive ID tag 135 present inside the product 130, and reads theconductive ID tag 135 based on the reflection wave signal 145. Theconductive ID tag 135 includes a barcode 137 recorded in a conductiveink. The radar transceiver 110 may form a radar image of the barcode 137based on the reflection wave signal 145 and trace the product 130.

As such, the use of the short-range mmWave radar enables identificationof the presence or absence of a product inside a box wrapped in thefactory or the positioning of a particular book in a library. In otherwords, a low-cost, non-destructive chipless RFID system may beimplemented which can extract a synthesis aperture radar (SAR) imageusing the nature of a radar signal that it can be transmitted through awrapping material.

FIG. 2 is a view illustrating operations of a radar transceiveraccording to an embodiment of the present disclosure.

Referring to FIG. 2, a conductive ID tag 220 present inside a box on aconveyor belt moves at a predetermined velocity in a predetermineddirection as the conveyor belt works. The conductive ID tag 220 becomesa target object that is intended to be detected by a radar transceiver210. The radar transceiver 210 detects the moving conductive ID tag 220at different positions while remaining at a fixed position. In theexample shown, the radar transceiver 210 detects a first reflection wavesignal 230 for the conductive ID tag 220 at a first position, a secondreflection wave signal 232 for the conductive ID tag 220 at a secondposition, and a third reflection wave signal 234 for the conductive IDtag 220 at a third position. The conductive ID tag 220 includes abarcode 225, which is recorded in a conductive ink and operates as pointscatters for a signal sent from the radar transceiver 210, and eachreflection wave signal include reflection signals for the point scatterscorresponding to lines in the barcode 225. The radar transceiver 210then detects the positions of the lines constituting the barcode 225based on the signal strengths and phases of the reflection signalsincluded in the reflection wave signals.

FIG. 3 is a view illustrating a tag cross-polar electromagnetic (EM)image detected by a radar transceiver according to an embodiment of thepresent disclosure. Here, the horizontal axis denotes the azimuth orcross-range, and the vertical axis denotes the range. Here, ‘range’means the length in an axis direction of the line connecting the radarwith the center of a target, and ‘cross-range’ means the length in adirection perpendicular to an axis of the range.

Referring to FIG. 3, an EM image 310 includes code images formattedcorresponding to the lines of the barcode 225 in the conductive ID tag220. Here, the horizontal axis means the width of the conductive ID tag220 or cross-range, and the vertical-axis range means the length of theconductive ID tag 220. The code images include the signal strengths andphases of reflection wave signals detected at different line positionsof the conductive ID tag 220. The radar transceiver 210, according topredetermined intervals (0.3 cm intervals in the example shown), maydetermine that the line position where a code image is detected is code1, and the line position where no code image is detected is code 0.

Here, the code recognition rate may sharply be lowered due to thedifference in reflection signal strength that stems from differences indistance (or also referred to as range) between the radar and the lines.In the following embodiments, thus, the reflection signal strengths arecompensated given, e.g., the difference in distance between the radarand the target and antenna radiation patterns which are a cause for aRCS distortion in the short-range radar system.

A radar image of a target object may be formed based on RCSs calculatebased on multiple reflection wave signals reflected on the targetobject. Here, the radar transceiver may determine times of scanning thereflection wave signals in order to measure the reflection wave signalsequiangularly with respect to the radar transceiver. According to anembodiment of the present disclosure, where a target object fordetection is on the move along a predetermined moving line, such as afactory conveyor belt does, different methods for determining the timeof scanning the target object may be set depending on the movingvelocity of the conveyor belt.

In order to synthesize a radar image of a conductive ID tag embedded (orattached onto the outside of) a box moving along a predetermined movingline, a mmWave radar system having a single transceiver may be operatedin the following sequence to measure equiangular reflection wave signalswith respect to the radar system.

The minimum distance r between the radar system and the moving line ispreviously known to the radar system upon placing the radar system andthe conveyor belt.

At some time t₀ (initial measurement time), the radar system, aftertransmitting a radar signal, receives a reflection wave signal. Thedistance d₀ from the target object and the moving velocity v₀ on themoving line are obtained based on the received reflection wave signal.In this case, the moving velocity v₀ on the moving line may be obtainedfrom an actually measured velocity v₀ ^(raw) on the line of transmissionand reception by the radar, as follows:

$\begin{matrix}{v_{0} = {\frac{d_{0}}{\sqrt{d_{0}^{2} - r^{2}}}v_{0}^{raw}}} & {{Equation}\mspace{14mu} 1}\end{matrix}$

When the number of times of measurement required to synthesize a radarimage of the target object is 2n+1, measurement times when reflectionwave signals for the target object are to be scanned may be obtained inthe following order based on results obtained at the initial measurementtime.

When the distance between positions on the moving line at measurementtime t_(k) is defined with respect to the position closest to the radarsystem, the distance is calculated as in Equation 2 below:

$\begin{matrix}{{l_{k} = {r \cdot {\tan \left( {\frac{{n - k}}{n}{\cos^{- 1}\left( \frac{r}{d_{0}} \right)}} \right)}}},{k = 0},1,2,3,\ldots \mspace{14mu},{2n}} & {{Equation}\mspace{14mu} 2}\end{matrix}$

Measurement times t_(k) after the initial measurement time may becalculated as in Equation 3 below:

$\begin{matrix}{{t_{k} = {\frac{{l_{k} - l_{k - 1}}}{v} + t_{k - 1}}},{k = 1},2,3,\ldots \mspace{14mu},{2n}} & {{Equation}\mspace{14mu} 3}\end{matrix}$

Here, v means the constant moving velocity of the target object on themoving line, which is determined to be a velocity (v₀) measured for thetarget object at the initial measurement time. r is the minimum distancebetween the radar system and the target object, which is a valuepreviously known to the radar system upon placing the radar transceiver.d₀ means the distance between the radar system and the target objectwhich is measured for the target object at the initial measurement time.

FIG. 4 is a view illustrating an operation of determining a scan time ofa target moving at a constant velocity in a radar system according to anembodiment of the present disclosure.

Referring to FIG. 4, a radar transceiver 410 has a fixed position, and atarget object 420 is moving at a constant velocity along a predeterminedmoving line of a conveyor belt 405. When 2n times of measurement arerequired to generate a radar image for the target object 420 after atime t₀ when the target object 420 is first scanned—i.e., the initialmeasurement time, each time of measurement may be calculated as inEquation 3 above. Here, n is a positive integer which may previously bedetermined by the system operator or designer.

As per Equation 3 above and using a predetermined value, n, the initialmeasurement time, distance, and velocity, 2n scan times t₁, t₂, t₃, t₄,t₅, . . . , t_(2n) are sequentially calculated in real-time. The radartransceiver 410 may repeat the operations of transmitting radar signalsto the target object 420 at the scan times, respectively, and receivingreflection wave signals corresponding to the sent-out signals and maythus gather the distance d_(k) from the target object 420, velocityv_(k) (k=1, 2, 3, . . . , 2n) at each scan time and reflection signalstrengths, while remaining equiangular.

FIG. 5 is a view illustrating an operation of determining a scan time ofa target moving at a variable velocity in a radar system according to anembodiment of the present disclosure.

Referring to FIG. 5, a radar transceiver 510 has a fixed position, and atarget object 520 is moving along a predetermined moving line of aconveyor belt 505. The velocity of the target object 520 may be varied.

When some time to is a time when the target object 520 is firstscanned—i.e., the initial radar measurement time—and 2n times ofmeasurement are required to generate a radar image for the target object520, each time of measurement may be calculated as in Equation 2 above.Here, n is a positive integer which may previously be determined by thesystem operator or designer.

$\begin{matrix}{{t_{k} = {\frac{{l_{k} - l_{k - 1}}}{v_{k - 1} + {\left( {v_{k - 1} - v_{k - 2}} \right)/2}} + t_{k - 1}}},{k = 1},2,3,\ldots \mspace{14mu},{2n}} & {{Equation}\mspace{14mu} 4}\end{matrix}$

Here, v_(k−1) means the moving speed of the target object 520 asmeasured at scan time t_(k−1), and v₀ is determined to be a velocitymeasured for the target object 520 at the initial radar measurementtime. r is the minimum distance between the radar transceiver 510 andthe target object 520, which is a value previously known to the radartransceiver 410 upon placing the radar transceiver 510 and the conveyorbelt 505. d₀ means the distance between the radar transceiver 510 andthe target object 520 which is measured for the target object 520 at theinitial radar measurement time.

As per Equation 4 above and using a predetermined value, n, the initialmeasurement time, distance, and velocity, 2n scan times t₁, t₂, t₃, t₄,t₅, . . . , t_(2n) are sequentially calculated in real-time. The radartransceiver 510 may repeat the operations of transmitting radar signalsto the target object 520 at the scan times, respectively, and receivingreflection wave signals corresponding to the sent-out signals and maythus gather the distance d_(k) from the target object 520, velocityv_(k) (k=1, 2, 3, . . . , 2n) at each scan time and reflection signalstrengths, while remaining equiangular.

FIG. 6 is a block diagram illustrating a brief structure of a radarsystem according to an embodiment of the present disclosure.

Referring to FIG. 6, a radar system includes a radar transceiver 620that transmits radar signals through an antenna 630 and receivesreflection wave signals corresponding to the sent-out signals and aprocessor 610 that reads a target object according to a result ofdetecting the reflection wave signals by the radar transceiver 620. Theprocessor 610 may calculate reflection signal strengths according to theresult of detecting the reflection wave signals, compensate for thereflection signal strengths, and form code images as per the compensatedreflection signal strengths, according to an embodiment of the presentdisclosure.

FIG. 7 is a view illustrating differences in reflection signal strengthdue to distances between a shrunken running screen and a target objectaccording to an embodiment of the present disclosure.

Referring to FIG. 7, a radar transceiver 710 transmits radar signals toa target object 720, e.g., a conductive ID tag, receives reflection wavesignals scattered by the target object 720, and measures reflectionsignal strengths for the target object 720 based on the reflection wavesignals. The minimum distance between the radar transceiver 710 and thetarget object 720 is R^(R), and the maximum distance therebetween is√{square root over (R²+d²)}. Here, d is ½ of the width of the targetobject 720. As an example, d may be previously known to the radartransceiver 710 by, e.g., the specifications of the conductive ID tag ormay be actually measured upon synthesize of an initial radar image.

Among a plurality of line codes constituting the conductive ID tag ofthe target object 720, line codes more distant from the center thereofpresent smaller reflection signal strengths than those of line codescloser to the center because of being further away from the short-rangeradar transceiver 710, although they are of the same length. Hence, thereflection signal strength measured for an i^(th) line code from thecenter of the plurality of line codes constituting the conductive ID tagmay be compensated as in Equation 5 below depending on the difference indistance between the center of the target object 720 and the i^(th) linecode.

$\begin{matrix}{{\overset{\sim}{A}\left( d_{i} \right)} = {{A\left( d_{i} \right)}\left( \frac{\sqrt{\left( {R^{2} + d_{i}^{2}} \right)}}{R} \right)^{4}}} & {{Equation}\mspace{14mu} 5}\end{matrix}$

Here, A(d_(i)) means the reflection signal strength measured for thei^(th) line code of the target object 720 by the radar transceiver 710,and d_(i) means the distance between the central point and the i^(th)line code.

FIG. 8 is a view illustrating differences in reflection signal strengthdue to antenna radiation patterns in a shrunken running screen accordingto an embodiment of the present disclosure.

Referring to FIG. 8, a radar transceiver 810 forms a lobe 830representing an antenna radiation pattern towards a target object 820,e.g., a conductive ID tag. The antenna gain for the line code positionedat the center of the target object 820 is a₀, and the antenna gain forthe i^(th) line code from the center is a_(i). By the nature of theantenna radiation pattern 830, line codes more distant from the centerof the plurality of line codes constituting the conductive ID tagexhibit smaller antenna gains than those of line codes closer to thecenter. Such a difference in antenna gain increases as the object widensrelative to the distance from the target object 820. Accordingly, thereflection signal strength measured for the i^(th) line code of thetarget object 820 according to the difference in antenna gain may becompensated as in Equation 6 below:

$\begin{matrix}{{\overset{\sim}{A}\left( d_{i} \right)} = {{A\left( d_{i} \right)}\frac{a_{0}}{a_{i}}}} & {{Equation}\mspace{14mu} 6}\end{matrix}$

The antenna radiation pattern 830, as a value given upon designing theantenna, is previously known to the radar transceiver 810.

Since the difference in reflection signal strength due to distance andthe difference in reflection signal strength due to antenna radiationpattern arise independently from each other, the compensation for areflection signal strength may be achieved as in Equation 7 below, whenboth the factors are taken into consideration.

$\begin{matrix}{{\overset{\sim}{A}\left( d_{i} \right)} = {{A\left( d_{i} \right)}\left( \frac{\sqrt{\left( {R^{2} + d_{i}^{2}} \right)}}{R} \right)^{4}\frac{a_{0}}{a_{i}}}} & {{Equation}\mspace{14mu} 7}\end{matrix}$

FIG. 9 is a flowchart illustrating a code reading procedure using ashort-range mmWave radar system according to an embodiment of thepresent disclosure.

Referring to FIG. 9, a radar system transmits radar signals to a targetobject and receives reflection wave signals corresponding to thesent-out signals to detect the target object in operation 910. Here, thetarget object may be, e.g., a conductive ID tag present inside a box orattached to the outside of the box. The conductive ID tag may include abarcode recorded in a conductive ink. The box with the target objectattached thereto is on the move, e.g., on a conveyor belt.

According to an embodiment of the present disclosure, before receivingthe reflection wave signals, e.g., where a reflection wave signalcorresponding to the target object is first received, the radar systemmay designate, as an initial measurement time, the time when the radarsignal corresponding to the reflection wave signal was sent out andcalculate in real-time measurement times when to scan the reflectionwave signals for the target object based on the distance and velocitydetected for the target object at the initial measurement time. By wayof example, the measurement times may be calculated as per Equation 3 or4 above.

Information about whether the target object moves at a constant velocityor variable velocity may be previously known to the radar system uponinstallation of a mover (e.g., the conveyor belt) of the target objector by the system designer or system operator, or may be determineddirectly by the radar system performing measurement on the target objectat least three or more times.

In operation 915, the radar system extracts reflection signal strengthsfor the plurality of line codes constituting the target object based onthe reflection wave signals detected at the plurality of measurementtimes. Here, where a radar image for the target object is formed byconducting SAR processing using the extracted reflection signalstrengths as they are, the code recognition rate may sharply be lowereddue to the difference in reflection signal strength between the linecodes. To address such issue, a compensation procedure, such as at leastone of operations 920 to 935 described below, may be carried out.Operations 920 and 935 described below may be selectively or integrallyapplied depending on the system designer's or operator's choice.

In operation 920, the radar system may calculate an angle on the antennaradiation pattern using the distance R between the radar system and thetarget object and the distance d_(i) between the center of theconductive ID tag and the i^(th) line code from the formed radar image.In operation 925, the radar system may compensate for reflection signalstrengths of the reflection wave signals measured for each line code ofthe target object based on the distances. As an example, the reflectionsignal strength compensation, operation 925, may be fulfilled as perEquation 5 above.

In operation 930, the radar system may perform compensation, as per theantenna radiation pattern, on the reflection signal strengths measuredfor each line code or the reflection signal strengths compensated inoperation 925. Here, the antenna radiation pattern is information thatmay be known in advance by measurement when the radar system is builtup. For compensation as per the antenna radiation pattern, the radarsystem first calculates the angle for each line code from the distancebetween the radar system and the target object detected in operation910, determines an antenna gain on the antenna radiation pattern foreach line code based on the calculated angle, and compensates for thereflection signal strengths for each line code based on the antennagain. As an example, the reflection signal strength compensation,operation 930, may be fulfilled as per Equation 6 above.

Since the compensation operations 925 and 930 are independent of eachother, the compensation operation 925 as per distance and thecompensation operation 930 as per antenna radiation pattern maysimultaneously be performed using Equation 7.

A radar image of the target object, which is formed based on thereflection signal strengths compensated via operation 925 and/oroperation 930, may have a uniform radar cross section (RCS) per linecode.

Operation 935 may reduce errors in reading codes for the RCSs of theline codes through a threshold adaptation procedure. In an embodiment,the adaptation procedure may be performed as follows.

Each pixel value of a radar image formed based on gathered reflectionwave signals is calculated by accruing the power strengths of thereflection wave signals corresponding to a relevant point in the targetobject for a plurality of measurement times. Where the distribution ofthe power strengths is large, invalid values need to be removed from thepower strengths of the pixels. To that end, there is a need for theprocess of forcing pixels having power strengths less than a thresholdinto zero to reinforce the accuracy of the radar image. In this case,the warehouse or manufacturing factory, which is under real-timeoperation, needs to have a threshold that adaptively responds each timefor various wrapping boxes.

In operation 935, the radar system may calculate an adaptive thresholdas in Equation 8 below depending on the distribution of power strengthsin the adaptation procedure.

Th=P _(max) −α×E{|P−E{P}| ²}  Equation 8

Here, P, as a random variable, includes values constituted depending ona probability distribution based on reflection signal strengthscorresponding to the pixels of the radar image. The values constitutingthe random variable, P, are ones obtained with the power strengths ofthe reflection wave signals measured for the radar image pixels. P_(max)means the maximum value of all the pixel values of the radar image, andα means a predetermined scalability factor.

When an adaptation threshold as per the distribution of power strengthsis calculated, the radar system deletes pixel values less than theadaptation threshold from the pixel values constituting the radarimage—i.e., sets them into zero—to thereby any lack of clarity of theline images.

In operation 940, the radar system applies the adaptation threshold tofinally form a radar image and reads a binary code from the radar image.

FIGS. 10A, 10B, and 10C are views illustrating a correction procedure ofa radar image according to an embodiment of the present disclosure.Here, the horizontal axis means the azimuth or cross-range (the width ofthe conductive ID tag), and the vertical axis means the range (thelength of the conductive ID tag).

Referring to FIG. 10A, a radar image 1010 is illustrated prior to theapplication of threshold adaptation, wherein the radar image 1010 shownis formed based on integrated values of reflection signal strengths forreflection wave signals gathered at multiple times. As shown, brief lineimages, although included in the radar image 1010, are unclear for theircontour, rendering it difficult to precisely read out a binary codecorresponding to the line images.

Referring to FIG. 10B, a radar image 1020 obtained by applying anadaptation threshold to an initial radar image 1010 is illustrated,according to an embodiment of the present disclosure, wherein the radarimage 1020 contains clearer line images than the radar image 1010 ofFIG. 10A.

Referring to FIG. 10C, a radar image 1030 obtained by applying both thecompensation as per distance and the compensation as per antennaradiation pattern is illustrated according to an embodiment of thepresent disclosure. In other words, the radar image 1030 shown is onegenerated by applying compensation as per distance and compensation asper antenna radiation pattern to the radar image 1020 of FIG. 10B. Asshown, the radar image 1030 creates line images easier to read outbecause the maximum power strength of each code line becomes similar, ascompared with the radar image 1020 that has not gone through thecompensation as per distance and compensation as per antenna radiationpattern.

FIG. 11 is a view illustrating a procedure of reading a binary code froma compensated radar image according to an embodiment of the presentdisclosure.

Referring to FIG. 11, reference number 1110 is a conductive ID tag, as atarget object, constituted of line codes recorded in a conductive ink.Reference number 1120 indicates a radar image generated based onreflection wave signals for the target object. As shown, the radar imageincludes line images at predetermined intervals. Reference number 1130means a binary code read out based on the radar image. The radar imagedetermines that line positions where a line image is present in theradar image are 1's, and line positions where no line image is presentare 0's. A binary code read out that way becomes “11101101” as in theexample shown.

The above-described embodiments remove a substantial deterioration ofdetection performance of a mmWave radar system with short-rangedetection coverage of a few meters or less, due to a RCS distortion thatarises in the radar system. In other words, the above-describedembodiments propose compensation schemes capable of canceling outfactors that may cause a RCS distortion, contributing to increasedusability of the short-range radar system.

Particular embodiments of the present disclosure may be implemented ascomputer readable codes in a computer readable recording medium. Thecomputer readable recording medium is a data storage device that maystore data readable by a computer system. Examples of the computerreadable recording medium may include read only memories (ROMs), randomaccess memories (RAMs), compact disc-read only memories (CD-ROMs),magnetic tapes, floppy disks, optical data storage devices, and carrierwaves (such as data transmission over the Internet). The computerreadable recording medium may be distributed by computer systems over anetwork, and accordingly, the computer readable codes may be stored andexecuted in a distributed manner Functional programs, codes, and codesegments to attain various embodiments of the present disclosure may bereadily interpreted by skilled programmers in the art to which thepresent disclosure pertains.

Certain aspects of the present disclosure can also be embodied ascomputer readable code on a non-transitory computer readable recordingmedium. A non-transitory computer readable recording medium is any datastorage device that can store data which can be thereafter read by acomputer system. Examples of the non-transitory computer readablerecording medium include a Read-Only Memory (ROM), a Random-AccessMemory (RAM), Compact Disc-ROMs (CD-ROMs), magnetic tapes, floppy disks,and optical data storage devices. The non-transitory computer readablerecording medium can also be distributed over network coupled computersystems so that the computer readable code is stored and executed in adistributed fashion. In addition, functional programs, code, and codesegments for accomplishing the present disclosure can be easilyconstrued by programmers skilled in the art to which the presentdisclosure pertains.

At this point it should be noted that the various embodiments of thepresent disclosure as described above typically involve the processingof input data and the generation of output data to some extent. Thisinput data processing and output data generation may be implemented inhardware or software in combination with hardware. For example, specificelectronic components may be employed in a mobile device or similar orrelated circuitry for implementing the functions associated with thevarious embodiments of the present disclosure as described above.Alternatively, one or more processors operating in accordance withstored instructions may implement the functions associated with thevarious embodiments of the present disclosure as described above. Ifsuch is the case, it is within the scope of the present disclosure thatsuch instructions may be stored on one or more non-transitory processorreadable mediums. Examples of the processor readable mediums include aROM, a RAM, CD-ROMs, magnetic tapes, floppy disks, and optical datastorage devices. The processor readable mediums can also be distributedover network coupled computer systems so that the instructions arestored and executed in a distributed fashion. In addition, functionalcomputer programs, instructions, and instruction segments foraccomplishing the present disclosure can be easily construed byprogrammers skilled in the art to which the present disclosure pertains.

Accordingly, the present disclosure encompasses a program containingcodes for implementing the device or method set forth in the claims ofthis disclosure and a machine (e.g., computer)-readable storage mediumstoring the program. The program may be electronically transferred viaany media, such as communication signals transmitted through a wired orwireless connection and the present disclosure properly includes theequivalents thereof.

The apparatuses according to various embodiments of the presentdisclosure may receive the program from a program providing devicewiredly or wirelessly connected thereto and store the same. The programproviding apparatus may include a memory for storing a program includinginstructions enabling a program processing apparatus to perform a methodaccording to an embodiment of the present disclosure and data necessaryfor a method according to an embodiment of the present disclosure, acommunication unit for performing wired or wireless communication with agraphic processing apparatus, and a controller transmitting the programto the graphic processing apparatus automatically or as requested by thegraphic processing apparatus.

While the present disclosure has been shown and described with referenceto various embodiments thereof, it will be understood by those skilledin the art that various changes in form and details may be made theretowithout departing from the spirit and scope of the present disclosure asdefined by the appended claims and their equivalents.

1. A method for identifying an object using a short-range millimeterwave (mmWave) signal in an electronic device, the method comprising:transmitting a mmWave signal to the object; receiving reflection wavesignals reflected from a plurality of points on the object in responseto the transmitted mmWave signal; obtaining reflection signal strengthscorresponding to the plurality of points on the object based on thereceived reflection wave signals; compensating the obtained reflectionsignal strengths based on a difference in an antenna gain between theplurality of points according to a radiation pattern of the mmWavesignal; and identifying the object using the compensated reflectionsignal strengths.
 2. The method of claim 1, wherein a transmissiondistance of the mmWave signal corresponding to each of the plurality ofpoints is different.
 3. The method of claim 1, further comprisingdetermining a transmission period of the mmWave signal based on aninitial measurement time and a moving speed of the object.
 4. The methodof claim 1, wherein the antenna gain is smaller than a point far from acenter of the plurality of points than a point near the center.
 5. Themethod of claim 1, wherein the identifying of the object comprises:calculating a threshold for signal strength corresponding to pixels on aradar image of the object based on a distribution of the compensatedreflection signal strengths; and setting one or more compensated signalstrengths less than the threshold for the signal strength among thecompensated reflection signal strengths to zero.
 6. An electronic deviceidentifying an object using a short-range millimeter wave (mmWave)signal, the electronic device comprising: a transceiver configured to:transmit a mmWave signal to the object, and receive reflection wavesignals reflected from a plurality of points on the object in responseto the transmitted mmWave signal; and at least one processor configuredto: obtain reflection signal strengths corresponding to the plurality ofpoints on the object based on the received reflection wave signals,compensate the obtained reflection signal strengths based on adifference in an antenna gain between the plurality of points accordingto a radiation pattern of the mmWave signal, and identify the objectusing the compensated reflection signal strengths.
 7. The electronicdevice of claim 6, wherein a transmission distance of the mmWave signalcorresponding to each of the plurality of points is different.
 8. Theelectronic device of claim 6, wherein the at least one processor isfurther configured to determine a transmission period of the mmWavesignal based on an initial measurement time and a moving speed of theobject.
 9. The electronic device of claim 6, wherein the antenna gain issmaller than a point far from a center of the plurality of points than apoint near the center.
 10. The electronic device of claim 6, wherein theat least one processor is further configured to: calculate a thresholdfor signal strength corresponding to pixels on a radar image of theobject based on a distribution of the compensated reflection signalstrengths, and set one or more compensated signal strengths less thanthe threshold for the signal strength among the compensated reflectionsignal strengths to zero.